Although the Actinomycetales produce more than half of the known antibiotics having valuable clinical and other applications as secondary metabolites and, thus, are recognized as a key target for application of gene manipulation techniques, many problems remain to be overcome before specific useful genes are successfully identified and cloned ["Molecular Breeding and Genetics of Applied Microorganisms", Sakaguchi and Okanishi, eds., Academic Press (New York) Kodansha Ltd. (Toyko) 1980, pgs. 130-131]. Until the present work, cloning of a .beta.-galactosidase gene from a Streptomyces species onto a suitable vector followed by introduction and expression of such vector has not been reported. Prior work has concerned development of other cloning systems or vectors for Streptomycetes [Bibb et al. (1978), Nature 274: 398-400; Hayakawa et al. (1979), J. Antibiot. XXXII(12): 1348-1350; Okanishi et al. (1980), J. Antibiot. XXXIII(1): 88-91; Bibb et al. (1980), Nature 284: 526-531; Thompson et al. (1980), Nature 286: 525-527; Suarez et al. (1980), Nature 286: 527-529; Bibb et al. (1981), Mol. Gen. Genet. 184: 230-240]; Bibb (1981), "Microbiology-1981", Schlessinger, ed., American Society for Microbiology, (Washington, D.C.) 1981, pgs. 367-370 and Hopwood et at. (1981), "Microbiology-1981", supra. pgs. 376-379], cloning and expression in Streptomyces sp. of genes derived from Escherichia coli [Schottel et al. (1981), J. Bacteriol. 146: 360-368] and cloning of genes from Streptomycetes in Escherichia coli ["Molecular Breeding and Genetics of Applied Microorganisms", supra; pgs. 130-137]. Chater et al. (1982), Current Topics in Microbiol. and Immunol. 96: 69-95, review gene cloning in Streptomyces and is incorporated by reference herein as though fully set forth.